WASHINGTON/DUBAI/TEL AVIV, April 9 - U.S. President Donald Trump vowed to retain military assets in the Middle East until a peace deal with Iran is reached and warned of a major escalation in fighting if it failed to comply, as oil prices rose on concerns over supply and restrictions in the Strait of Hormuz.

Trump said in a social media post U.S. ships, aircraft and personnel with additional ammunition and weaponry would remain in place to destroy, if necessary, "a substantially degraded enemy", but expressed confidence that a lasting deal would be agreed and followed.

"If for any reason it is not, which is highly unlikely, then the 'Shootin’ Starts,' bigger, and better, and stronger than anyone has ever seen before," Trump said, adding that contrary to "fake rhetoric", Iran had agreed not to pursue nuclear weapons and to reopen the Strait of Hormuz.

"In the meantime our great Military is Loading Up and Resting, looking forward, actually, to its next Conquest. AMERICA IS BACK!"

Though both the United States and Iran declared victory in a five-week-old war that has killed thousands, their core disputes remained unresolved, with each side sticking to competing demands for a deal that could shape the Middle East for generations.

IRAN SAYS TALKS 'UNREASONABLE' AMID ISRAELI STRIKES

Trump's latest post followed the largest coordinated strike of the war by Israel on Wednesday that killed more than 250 people in Lebanon, prompting a warning from Iran's lead negotiator that Israel's ramping up its parallel war and Washington's insistence on Tehran abandoning its nuclear ambitions could jeopardise talks to forge a permanent peace deal.

"In such a situation, a bilateral ceasefire or negotiations were unreasonable," Iran's parliament speaker Mohammed Bager Qalibaf, said in a statement on Wednesday.

Oil prices climbed on Thursday with investors concerned about the fragility of the truce and elevated geopolitical risks over Middle East supply, with doubts that restrictions in the Strait of Hormuz would soon ease.